Telephone



(No Model.)

, UNrrnn STATES A Armat* tries,

FRANCS BLAKE, OF WESTON, MASSACHUSETTS.

TELEPHQNE.

.CPECIPICATION "ormng pari: of Letters Patent No. 31-'=,312= dated March 24, 1885.

Application filed Fvbrnary 9, 1885. (No model IO LZZ whom'i may ormcern:

Be it known that I, FRANcis BLAKE, of Weston, Massachusetts, have invented a new and useful Improvement in Speaking-Telephones, of which the following is a specification. i-

The invention relates to that class of telephone-transmittcrs in which a p/owdored or granulated conducting material forms that portion of the telephone-circuit the resistance of which is varied under the action of sound- Waves. I enploy a horizontal diaphragm which receives the sound-Waves upon its under surface, and has a mass of powdered or granulated conducting material lyiug loosely upon its upper surface and forming the variable-resistance portion of the circuit. A mass of such material in a loose condition has a very high resistance as com pared with the same mass in a solid or compact form, and the vibrations of the diaphragm under the action of sound-Waves tend constantly to throw the loose conducting material upward and prevent it from beconing so compacted or compressed as to change the specific resistance of the mass.

One part of the invention relates to the construction of an electrode which is buried in the granulated material and admits such free movement thereof, and at the sametime gives a large cross-section, and consequently a comparatively low resistance, to that part of the circuit. I am thus enabled to accomplish results with a single cell of battery which might otherwise require a larger nunber of cells.

Another part of my invention relates to a method of Connecting the diaphragm with the electrode which is buried in the loose material, so that the diaphragm is strained, and so that the vibrations of the diaphragm shall affect the loose material more uniformly, and shall be comniunicated directly to said buried electrode. An unstrained diaphragm, by reason, probably, of differences of tension between different portions, is liable to vibrate differently under the action of sound-Waves at different points equally distant from the center, and thus may fail to cause changes in the resistance of the loose material corresponding faithfully to the form of the sound-Waves; The vibrations of the electrode due to its mechanical connection with the diaphragm assist in maintaining the loose condition of the granulated material.

In the drawings, Figure 1 is asectional elevation of my new transmitter embodying the above-mentioned improvements. Fig. 2 is a plan of the same with the clamping-plate and the granulated conductor omitted.4 Fig. 3 is aplan of the diaphragm. Fig. 4 is a plan of the sieve electrode. Fig. 5 isa plan of a nonconductng washer used to separate the diaphragn from the sieve electrode. Fig. 6 is a plan of a non-conducting post or block inserted between the diaphragm and the sieve electrode. Fig. '7 is a partial sectional elevation showing a modification.

All the parts are shown of full size, and I may add that after i much experimenting I have found that the size and p roportions shown are those best adapted for the nse of the instrument with ordinary receivers.

A is the bed or support for the telephone, and contains the aperture through which speech is uttered. i

B is a ring of non-conducting material resting on the bed A, and bis a metallic ring resting on the bed A within the ring B, and forming the seat of the diaphragm. In one form of construction the rings B and b are both of non-conducting material and are formed in one piece, the bed A in such case being omitted.

D is a metallic diaphragm, resting at its edg'es upon the ring orseat bt The diaphragm, as above stated, is one of the electrodes, and in practice it is connected with one of the circuit-wires through the seat b when that seat is metallic, or directly with such wire when the seat b is integral with the ring B and s of non-conducting material.

S is a wire sieve electrically sepa-rated from the diaphragm by a washer, w, of non-conducting material.

i Pis a netallic clanping-plate having a boss or ringprojection, p. that rests upon the sieve at the edges ot' the latter.

The plate P and the ring B ha've the same diameter, and so likewise the boss of the plate P, the sieve S, the washer w, the diaphragm D, and the seat b are equal in diameter; and accordingly the different parts of the instrument are held together by screws (I use but four) passing through the plate P and ring B,

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and into the bed A when a bed is employed. Electrical connection is made between the sieve electrode S and its circuit-wire through the metallic clamping-plate P.

O is a finely divided or granulated conducting material (I use powdered carbon) filling the-instrument above the diaphragm to within a short distance of the plate P. The grains are of a size that permits them to pass freely through the sieve, which is buried in their mass. The plate P has a hole through which the granulated conductorispoured. This hole is closed by a screW-plug, E.

L is a post or block ot' non-condueting material inserted between the diaphragm and the sieve, thereby straining` the diaphragm. It also gives to both the diaphragm and the sieve a conical form, and, being firmly clasped between the diaphragm and the sieve, as between two Springs, causes the latter mechanically to partake ofthe Vibrations of the forner.

When the instrument is connected up for use, as before stated, one wire leads to the diaphragm and the other to the sieve. The diaphragm and the sieve thus become electrodes, the granulated conductor making the electrical connection between them.

Further description of the mode of operation of the instrument as a whole is unnecessary. Y

The instrumentthus constructed will remain in adjustment, no matter what may be the character of the sounds falling upon the dia- 'phragm. Vocal sounds transmitted by it are remarkably faithful copies of the original, and, above all, the instrumentis superior to all other telephones with which I am acquainted W in preserving the loudness of the sounds transmitted. I will add,'however, that while the form of construction described and shown gives the best results as a whole I have found that some of the details of construction are advantageous to a greater or less extent independent of other details.

Thus the advantage derived from the action of a strained diaphragm acting upon loose material forming the variable-resistance portion of the circuit is not dependent upon the use of the diaphragm as one electrode, nor upon the use of the sieve as the other electrode, but will be secured when either the diaphragm or the sieve is used for one electrode, and a ring at the outer edge of the loose material is emy ployed as the other electrode-th at is, in the instrument shown one of the circuit-wires may be made to connect either with the diaphragm D or the sieve S, and the other with the bossp of the clamping-plate P; but when the sieve and the ring are made to serve as the electrodejs of the instrument represented in the drawings, they must be separated electrically by a washer. (For this construction see Fig. 7, where the additional washer is marked w'.) Neither is the advantage which is due to the mechanical connection between the sieve and the diaphragm Wholly dependent either upon the use of the diaphragm as an electrode or upon the use of the diaphragn in a horizontal position. There is great advantage gained as to loudness, even when the diaphragm is out of the circuit, by rigidly connecti ng the center of the diaphragm with the sieve buried in the loose condueting material, so that the sieve Will partake of the vibrations of the diaphragm, and this even if the instrument is turned up so as to be used substantially at a right angle to the position shown. Thepresent instrument may be so used by making the sieve serve as one electrode and the boss of the ring P as the other, inserting a non-condueting washer between them, and causing the sieve to partake of the vibrations of the diaphragm in the manner now shown.

I claiml. In a telephone employing a granulated condueting material as the variable-resistance portion of the circuit, two horizontal electrodes, one serving as the transmitting-diaphragm and carrying such material loosely upon its upper surface, and the other being a sieve buried in such material and allowing such material to pass freely through it, substantially as described.

2. In a telephone employig a granulated condueting material as the variahle-resistance port-ion of the circuit, two horizontal electrodes mechanically connected to vibrate together, one serving as the transmitting-daphragm and carrying such material loosely upon its upper surface, and the other being a I OO sieve buried in such material and allowing such material to pass freely through it, substantially as described.

3. In a contact-telephone employing granulated conducting material as the variable-resistance portion of the circuit, a transmittingdiaphragm in mechanical contact with said granulated material, and an electrode buried in said granulated material and allowing said material-to pass freely through it, the said electrode being mechanically connected to the said diaphragm at the center of the latter to partake of its vibrations, substantially as described.

4. In a telephone employing a granulated condueting material as the variable-resistance portion of the circuit, a transmitting-diaphragm carrying such material loosely upon its upper surface and strained to a conical form, substantially as described.

FRANOIS BLAKE.

W'itnesses:

W. V. SWAN, VM. S. RoGERs.

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